+ make model definition file use more config formats via load-config-file

lib/plugins/model.js

@@ -11,6 +11,7 @@ var debug = require('debug')('loopback:boot:model');
 var _ = require('lodash');
 var toposort = require('toposort');
 var utils = require('../utils');
+var loadConfig = require('load-config-file');
 
 var tryReadDir = utils.tryReadDir;
 var assertIsValidConfig = utils.assertIsValidConfig;
@@ -18,6 +19,8 @@ var tryResolveAppPath = utils.tryResolveAppPath;
 var fixFileExtension = utils.fixFileExtension;
 var g = require('../globalize');
 
+loadConfig.register('.json', JSON.parse);
+
 module.exports = function(options) {
   return new Model(options);
 };
@@ -186,7 +189,7 @@ function findModelDefinitions(rootDir, sources) {
 
     files
       .filter(function(f) {
-        return f[0] !== '_' && path.extname(f) === '.json';
+        return f[0] !== '_' && loadConfig.prototype.configurators[path.extname(f)] != null;
       })
       .forEach(function(f) {
         var fullPath = path.resolve(srcDir, f);
@@ -205,8 +208,8 @@ function findModelDefinitions(rootDir, sources) {
 }
 
 function loadModelDefinition(rootDir, jsonFile, allFiles) {
-  var definition = require(jsonFile);
   var basename = path.basename(jsonFile, path.extname(jsonFile));
+  var definition = loadConfig(basename);
   definition.name = definition.name || _.upperFirst(_.camelCase(basename));
 
   // find a matching file with a supported extension like `.js` or `.coffee`